In Patent Application Ser. No. 453,378, now abandoned, filed Mar. 21, 1974, by Keith W. Tantlinger and assigned to the assignee of the present invention, a joint of the general type shown in FIG. 1 is disclosed. While the laterally opposed faces of the keyway shown in FIGS. 1 and 1a of that prior application are corrugated, the patent does not suggest or claim that these corrugations are not parallel to the keyway itself and since such corrugations are formed by the extruding die during the extrusion of the strake, they are of course, straight and uniform. In use and under test it has been found that these straight corrugations add little, if any, longitudinal shear strength to the joint.
The formation or deformation of these opposed keyway faces, preferably in a sinous wave or interrupted thread pattern is the subject matter of the present invention. While the mere use of a strong, bonding type plastic key material provides, in the structure of said patent, a joint of substantial strength in all directions including longitudinal shear, the present invention greatly increases this longitudinal shear strength, an important factor in Transit vehicles of the type for which this joint is intended.